1. LASERS & LASER PROTECTION

2. LASERS & LASER PROTECTION
Objectives
1. Describe military uses for lasers
2. Describe the four laser classifications
3. Describe laser effects on the eye and skin
4. Identify the two goals of laser eye protection
5. Identify the shortfalls of laser eye protection
The lesson objectives are to describe the military uses of lasers, the four laser classifications, and the effects of lasers on the eyes and skin; and to identify the two goals and shortfalls of laser eye protection.

3. LASERS & LASER PROTECTION
Definition
LASER:
Light Amplification by Stimulated Emission of Radiation
A device that emits a highly-focused, single-wavelength beam of light
Its brightness can exceed that of all known natural sources
LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.
A laser produces a highly-focused, single-wavelength beam of light. This definition highlights the main differences between laser light and natural light: a laser beam is collimated and usually of one wavelength (i.e., color), whereas natural light diverges and usually contains a spectrum of wavelengths.
The brightness of a laser beam can exceed that of all known natural sources (such as the sun).

4. Military Uses of Lasers
LASERS & LASER PROTECTION
Military Uses of Lasers
Range Finding
Target Designation
Medical and Research
Training
Weapons
Damage enemy optical sensors and electronic equipment
Antipersonnel
Produce transient or permanent vision loss
The use of lasers by the military includes range finding, target designation, medical treatment, research, and training.
Laser weapons have also been developed. Some have been designed to destroy enemy optical sensors and other electronic equipment. And while prohibited by international law, some countries have build eye-damaging laser weapons. These are designed to produce transient or permanent vision loss.

5. Laser Classifications (ANSI Z 136.1 - 1993)
LASERS & LASER PROTECTION
Laser Classifications (ANSI Z )
Class 1
Intrinsically safe / No risk
No user precautions are required; no warning labels are necessary.
Example: grocery store scanner
There are four classes of lasers, 1 through 4.
Class 1 lasers are safe under virtually all viewing conditions. The beam is considered incapable of causing damage, and no warning labels are required.
An example of a Class 1 laser is the grocery store scanner.

6. Laser Classifications (ANSI Z 136.1 - 1993)
LASERS & LASER PROTECTION
Laser Classifications (ANSI Z )
Class 2
Low power / Low risk
Powerful enough to cause eye injury (but not to the skin) if the beam is deliberately viewed.
Blink reflexes will normally prevent injury.
A Caution Label is required.
Examples: laser pointers and construction lasers
Class 2 lasers are low-powered devices that emit only visible light. They are considered eye-safe unless there is a deliberate attempt to look into the beam for longer than 0.25 seconds. The blink reflex is normally quick enough to prevent laser-induced eye injury.
A CAUTION label is required on all Class 2 lasers.
Examples of Class 2 lasers are some laser pointers and construction lasers.

7. Laser Classifications (ANSI Z 136.1 - 1993)
LASERS & LASER PROTECTION
Laser Classifications (ANSI Z )
Class 3A
More powerful than Class 2, but are more spread out. Unmodified beams give no greater risk than Class 2.
Concentrated beams (for example by viewing it through binoculars) can cause injury in less than 0.25 seconds, the normal response time for blink reflexes.
A Caution Label is required.
Examples: laser pointers, and medical treatment and research lasers
Class 3 lasers are medium-powered devices. These are divided into two subclasses: 3A and 3B.
Class 3A lasers are more powerful than Class 2, but are more spread out. When unmodified, Class 3A lasers give no greater risk than Class 2. The beam may be eye-hazardous when collected and directed into the eye, as with binoculars.
A CAUTION label is required on all Class 3A lasers.
Examples of Class 3A lasers are some laser pointers, and medical and research lasers.

8. Laser Classifications (ANSI Z 136.1 - 1993)
LASERS & LASER PROTECTION
Laser Classifications (ANSI Z )
Class 3B
Medium power / Medium risk
Capable of causing eye injury; blink reflexes are too slow to respond.
A Danger Label is required.
Examples: weapon systems, and medical treatment and research lasers
Class 3B lasers are more powerful than Class 3A. These devices are capable of causing eye injury quicker than the blink reflex.
A DANGER label is required on all Class 3B lasers.
Examples of Class 3B lasers are some pointers, and weapon, medical and research lasers.

9. Laser Classifications (ANSI Z 136.1 - 1993)
LASERS & LASER PROTECTION
Laser Classifications (ANSI Z )
Class 4
High power / High risk
Capable of causing skin injury; skin covering recommended
Will instantly cause severe ocular injury (and possibly blindness). Even viewing beam reflections can cause eye injury.
Can cause combustion
A Danger Label is required.
Examples: weapon systems, medical
Class 4 lasers are high-powered devices which are hazardous to the skin. They can instantly cause severe ocular injury with direct OR reflected exposures. Class 4 lasers can be a fire hazard if used improperly.
A DANGER label is required on all Class 4 lasers.
Examples of Class 4 lasers are weapon system and medical lasers.

10. LASERS & LASER PROTECTION
Laser Light
Visible light forms just a small portion of the electromagnetic spectrum. Some laser beams fall within this visible spectrum.
Some laser beams fall into the ultraviolet or infrared spectrum. These beams are invisible to the naked eye.
Visible light is just a small portion of the electromagnetic spectrum. The light produced by some lasers falls within this visible range.
Other lasers emit invisible light that falls into the ultraviolet or infrared spectrum.

11. LASERS & LASER PROTECTION
Laser Light
The unit of light wavelength (color) is the nanometer
1 nm = 1/1,000,000 millimeter
Ultraviolet range ≈ nm
Visible range ≈ nm
Infrared range ≈ nm
The unit of wavelength is the nanometer (nm), which is equal to one millionth of a millimeter.
Ultraviolet light falls roughly between 100 and 380 nm.
Visible light falls roughly between 390 and 780 nm.
Infrared light falls roughly between 780 and one million nm.

12. LASERS & LASER PROTECTION
Laser Light
Most lasers produce beams of one wavelength only...
Argon Ion 488 nm (green)
HeNe 543 nm (yellow-green)
Ruby* 694 nm (red)
GaAs* 850 / 905 nm (invisible - infrared)
Nd:YAG* nm (invisible - infrared)
*Used extensively by the military
FYI: There will be “agile” lasers in the near future that can actively change their beam wavelength.
Most lasers produce only one wavelength of light. For example, the Argon Ion laser emits light at 488 nm, which is a greenish color. The Ruby laser emits light at 694 nm, which is a red color. The YAG laser emits light at 1064 nm, which is invisible to the naked eye.
The Ruby, GaAs (Gallium-Arsenic) and YAG lasers are used extensively by the military.
In the near future, there will be “agile” lasers; they will have the ability to change their beam wavelength “on the fly.” As we’ll see later in the brief, this causes some laser eye protection concerns.

13. LASERS & LASER PROTECTION
Laser Damage
Both visible and invisible laser beams can cause bodily injury.
This damage can be temporary or permanent
The eyes and skin are the most susceptible areas
The skin is most sensitive to ultraviolet and infrared wavelengths.
The result can be a “burn” or an increased chance of skin cancer
Its important to realize that BOTH visible AND invisible laser beams can be dangerous! The eyes and skin are the most susceptible, and the damage can be temporary or permanent.
The skin is most sensitive to ultraviolet and infrared wavelengths (which are both invisible). The result can be a “burn” or possibly an increased chance of skin cancer.

14. LASERS & LASER PROTECTION
Laser Damage
Ocular injuries from lasers are the largest concern.
The eye’s optics greatly concentrate the laser beam
Lasers can affect the eye by…
Producing glare / obscuring dim lights
Interfering with dark adaptation
Inducing flashblindness and afterimages
Causing temporary or permanent vision loss
Usually bilateral
Can be painless or painful
Eye injuries are the greatest laser concern. This is mainly because the optics of the eye greatly concentrate the laser beam.
Lasers can affect the eye by…
-Producing glare or obscuring dim lights (like Heads Up Displays),
-interfering with dark adaptation,
-inducing flashblindness and afterimages,
-and by causing temporary or permanent vision loss. This vision loss is usually bilateral and can be painless or painful.

15. LASERS & LASER PROTECTION
Laser Damage
The eyelid, like other skin, absorbs ultraviolet and infrared light. The cornea and lens absorb wavelengths above 1300 nm (far infrared). Lasers operating over these wavelengths can produce damage:
Eyelid “sunburns” or thermal burns
Corneal burns and scars
Cataracts
Like any skin, the eyelid absorbs ultraviolet and infrared light. The cornea and lens absorb wavelengths above 1300 nm. Lasers operating over these wavelengths can induce skin “sunburns” and thermal burns; corneal burns and scars; and lens cataracts.

16. LASERS & LASER PROTECTION
Laser Damage
The retina is exposed to wavelengths between ~390 and 1300 nm (visible and near infrared)
The eye’s optics collect and concentrate laser beams onto the retina. This can produce damage:
Thermal or photochemical retinal injury
Sub-retinal burns
Blood vessel hemorrhages
This injury can be painless...
There are no pain fibers in the retina
The retina is exposed to wavelengths between about 390 and 1300 nm. These are wavelengths in the visible and near infrared spectrums.
The eye’s optics collect and concentrate the laser beam onto the retina. This can cause:
-Thermal or photochemical retinal injury,
-sub-retinal burns,
-and blood vessel hemorrhages.

17. Laser Damage Healthy retina Retinal hemorrhage and burn
LASERS & LASER PROTECTION
Laser Damage
Healthy retina Retinal hemorrhage and burn
(secondary to Nd:YAG laser exposure)
The left photo illustrates a normal, healthy retina.
The right photo shows a laser-induced retinal hemorrhage and burn. This damage occurred very close to the person’s central vision. Immediately after the accident, his visual acuity was 20/800. Fortunately, this person recovered to almost 20/20 vision, but it took six months of extensive medical care.

18. LASERS & LASER PROTECTION
Laser Eye Protection
Laser eye protection (LEP) comes in many forms
Goggles, spectacles, visors...
LEP must be appropriate to the specific laser being used
Appropriate to its wavelength and power output
Lenses must be marked with wavelength and optical density
ANSI Z is the applicable standard
Obviously, laser eye protection is very important.
In the military, laser eye protection comes in many forms, such as goggles, spectacles and visors.
Laser eye protection must be appropriate to the specific laser being used! The eye must be protected against the laser’s wavelength and power output. Therefore, laser eye protection will be marked with a wavelength and optical density (i.e., level of light transmission).
ANSI Z136.1 of 1993 is the current standard for laser eye protection.

19. LASERS & LASER PROTECTION
Laser Eye Protection
At present, LEPs use one of two techniques:
(1) Reflective technology
(2) Filtering lenses
There are two overall goals in LEP:
Block (or reflect) the laser beam wavelength so it doesn’t reach the eye
Allow a maximum number of visible wavelengths to pass to the eye
Remember…“more light is more sight!”
At present, laser eye protection uses one of two techniques…
-Reflective technology,
-or filtering lenses.
The two overall goals of laser eye protection are to:
-Block (or reflect) a specific laser beam wavelength so it doesn’t reach the eye,
-and allow a maximum number of visible wavelengths to pass to the eye.
Remember, the more light reaching your retina, the better your vision…blocking too many wavelengths (i.e., too much light) can severely degrade vision

20. LASERS & LASER PROTECTION
Laser Eye Protection
Older LEP designs provide protection against one wavelength
Newer technology allows for multiple wavelength protection
Unfortunately, LEPs are not perfect...
A range of useful wavelengths can also be blocked
May slightly degrade daytime vision
May greatly degrade night vision
(like wearing sunglasses at night)
Colors can appear distorted
One LEP cannot protect you from all laser threats
Older versions of laser eye protection provide protection against one wavelength only. Through a mixture of filter pigments or lens coatings, newer versions allow for multiple (<3) wavelength protection.
As good as they are, laser eye protection devices are not perfect…
-A range of visible wavelengths can be blocked while attempting to block the laser light. This can slightly degrade daytime vision, and may greatly degrade night vision. Its similar to wearing sunglasses at night.
-Colors can be distorted
-At this time, one pair of laser eye protection cannot protect you from all potential laser threats! This is a real concern especially when dealing with the threat of “agile” lasers.

21. Laser Eye Protection - Practicalities
LASERS & LASER PROTECTION
Laser Eye Protection - Practicalities
When the threat wavelength is known, wear specific protection.
When the laser threat is unknown, wear multi-wavelength protection.
At night, the pupil dilates…
This increases the chance of internal eye damage from lasers.
Make sure to wear the appropriate LEP!
Never fixate on any target with laser-use potential… look to one side of it.
This minimizes the possibility of a central retinal burn and complete central vision loss.
What are some practicalities of laser eye protection?
-When the threat wavelength is known, wear the specific protection
-When the laser threat is unknown, wear multi-wavelength protection
-Remember that at night, the pupil dilates; this increases the chance that laser light can enter the eye. Be especially sure to wear the appropriate eye protection.
-Never fixate on any target with laser-use potential…always look to the side of it. This will minimize the possibility of a central retinal burn and complete central vision loss.

22. Laser Eye Protection - Practicalities
LASERS & LASER PROTECTION
Laser Eye Protection - Practicalities
Night Vision Goggles:
Some NVGs will provide laser eye protection, some will not.
Consult with your AMSO about your specific NVGs
Be prepared: lasers can easily produce temporary flashblindness through NVGs
If you are exposed to a laser beam, and cannot close both eyes (e.g., while flying an aircraft)…try to close one eye
This will help to prevent complete vision loss via bilateral flashblindness or eye injury.
Some Night Vision Goggles provide laser eye protection, some do not. Its best to consult with your AMSO about your specific NVGs.
NVGs are very sensitive to red and infrared wavelengths…they can be easily overwhelmed by laser beams. Be prepared…this can cause temporary flashblindness.
If you’re exposed to a laser beam (with unprotected eyes), but can’t close both eyes (e.g., while flying an aircraft), try to close one eye. This will help to protect the closed eye from flashblindness or eye injury.

23. Ocular Laser Overexposure
LASERS & LASER PROTECTION
Ocular Laser Overexposure
Suspected laser overexposures require IMMEDIATE action!
Seek medical attention...
Ocular history
Distance visual acuity
Color vision
Amsler grid
Slit lamp exam
Dilated retinal exam
Retinal photograph
If you suspect a laser overexposure to the eye, don’t hesitate to seek medical attention. Since these injuries can be painless and may not be associated with visual symptoms or complaints, it is important to get a full ocular examination.
-An ocular history will be taken, especially dealing with the laser exposure.
-Visual acuity will measured
-Color vision will be tested
-An Amsler grid (the grid shown on the right) will be used to test the uniformity of the central retina
-A microscope will be used to examine the eye
-The pupil will be dilated to allow for a full view of the retina
-And retinal photographs will be taken

24. Ocular Laser Overexposure
LASERS & LASER PROTECTION
Ocular Laser Overexposure
Contact one or more of the following ASAP:
Tri-Service Laser Incident Hotline ( )
The TVCR Team at USACHPPM ( )
The Laser Branch at USACHPPM ( )
CHPPM-EUR (DSN: )
Laser overexposures within the military are recorded, cataloged and analyzed. With an overexposure, one or more of these groups should be contacted ASAP.

25. Questions? Compiled and prepared by:
LT Tyson J. Brunstetter (OD, PhD), MSC, USNR
Naval Aerospace Medical Research Laboratory
Comm: x DSN:
Thank you to the following for supplying information and figures:
Edmund Industrial Optics (A Division of Edmund Scientific)
Gentex Corporation
Naval Air Warfare Center, Aircraft Division
Naval Operational Medical Institute, Ophthalmology/Optometry Dept.
Tri-Service Vision Conservation and Readiness Program
LT Michael Prevost, Aerospace Physiologist, NAMRL